The present invention relates to a paper tray which receives a stack of paper and can be inserted into a receiving device of a copying machine or the like, and which comprises a supporting plate for the stack of paper to which at least one spring is applied which lifts the supporting plate off the bottom of the tray.
Such paper trays are used for holding the paper sheets required for the pertaining machine available in the form of a stack, in which case the stack of sheets is lifted toward a paper feeding roller which, together with elements which follow, carries out the feeding of the paper and the separating of the sheets. Irrespective of the momentary height of the stack of sheets, this stack must always be at the same distance opposite the feeding rollers with the front edge of the uppermost sheet of the stack of paper, the stack facing the paper feeding device. For this reason, the stack of paper is held by a supporting plate which can be lifted off resiliently with respect to the bottom of the tray. For this purpose, it is known to mount one or several compression springs between the supporting plate and the bottom of the tray. When the tray is refilled with paper, the supporting plate must be pressed down against the force of the compression springs and the stack of paper must be inserted at the same time. In order to avoid a constant manual pressing-down during the inserting of the paper, it is known from the U.S. Pat. No. 4,280,692 to mount a locking mechanism for the supporting plate on the bottom of the tray. This locking mechanism locks the supporting plate after it was pressed down once and unlocks automatically when the tray is pushed into the machine.
It is an object of the invention to provide a paper tray of the initially mentioned type which has a simple construction and ensures a simple handling.
In the case of a paper tray of the initially mentioned type, this object is achieved in that a tensioning device is provided for the at least one spring to which a stop of the receiving device is assigned in such a manner that, when the tray is inserted into the receiving device, the spring can be tensioned and, when the tray is removed from the receiving device, it can be relaxed. As a result, the paper tray can be filled without any problems without the requirement of a manual pressing-down against the tensioning force of a spring. The spring, which lifts the supporting plate off the bottom of the tray, does not tighten, specifically automatically, before the paper tray is pushed into the machine.
In a further development of the invention, one tension spring respectively is pivotally connected on both sides to the supporting plate laterally next to the stack of paper. This tension spring can be tensioned and relaxed by means of one assigned tensioning device respectively. As a result, no components have to be mounted between the supporting plate and the bottom of the tray so that no minimum distance must be maintained between the supporting plate and the bottom of the tray. In its lowest position the supporting plate can therefore rest essentially flatly on the bottom of the tray which does not require any indentations, or the like. Since, for ensuring a secure sequence of operations, the supporting plate is arranged at a slight distance to the lateral walls of the tray anyhow, the tension spring arrangement otherwise also does not require any increased space. The arrangement of two tension springs, which are opposite one another, promotes a uniform lifting operation and avoids uneven lifting forces which may lead to a jamming of the paper.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.